| This experiment focused on improving coastal saline soil in Tianjin, with urban sewage sludge (W), cotton stalk powder (J), river sand (S) as modified material, setting single treatments (CK, J, W, S) and compound treatments (CK, J+W, J+S, W+S, J+W+S). All treatments had been conducted with and without pumice cushion layer, observated for three years. Indoor experiment was set as same as field experiment, but with bacterial manure in stead of pumice. Soil seed bank, plant-species, main salt ions, total salt, pH, organic matter concentration, above-ground biomass were observed, the aim was to enrich the coastal-saline-soil-amendmengt theory and practice by exploring effect of above amendments on coastal saline soil, and effect of vegetation restoration with the aid of amendments on saline soil measures. The main results were as follows:1. Compared with CK, concentration of calcium ion, potassium ion, magnesium ion, sulfuric acid ion increased significantly, on the contrary the concentration of other ions had been reduced. Chloride ions concentration had been reduced significantly. Main alkali bicarbonate ions declined significantly in three years. Extent of soil salt ion reduction of treatments laid pumice was greater than that of the treatments without pumice. The degree of ions reduction decreasesed according to the 0-10 cm,10-20 cm,20-30 cm,30-40 cm layers. The undulation of each ion in annual gradually reduced.2. Total salt reduced significantly. Soil total salt concentration laid pumice was lower significantly than that without pumice. Total salt of W, W+S, W+J, J+W+S were higher than CK in the first year, less than CK in the third year. Effect of treatment S for lowering total salt was better than treatment J. In terms of the effect of reducing total salt concentration, treatment J+S, S showed the best effect.3. The pH had been reduced significantly. The reducing effect expanded from 0-10 cm soil layer to 30-40 cm soil layer. The pH value laying pumice fell more than that without pumice. W lowered pH of 0-10 cm,10-20 cm, better than other single treatments; J+W, W+S, J+W+S lowered pH of 0-10 cm, 10-20 cm,20-30 cm,30-40 cm soil, better than other compound treatments. Treatment J+W+S showed the best effect for lowering pH.4. Organic matter concentrations of each treatment were increased significantly compared with CK, except treatment S. The order of organic concentration increased from large to small is:J+W+ S> J+W>W>W+S> J and J+S> S> CK. Organic matter concentration with pumice was more than that without pumice. Organic matter gradually reduced from the surface to the bottom, the organic matter concentration in 20-30 cm,30-40 cm soil were improved compared with CK, and the treatment J +W+S achieved the largest increase for organic matter concentration.5. Indoor experiment results showed that with the deepening of the soil nitrogen concentration increased gradually, while the phosphorus and carbon showed higher concentration in surface soil. Effect of sewage sludge for nutrient distribution in saline soil was obvious. The comprehensive utilization of organic matter and bacterial manure was helpful for increasing of carbon, nitrogen, phosphorus element in coastal saline soil, was helpful to reduce the soil electrical conductivity. Effect of treatment J+W+S showed the best effect to increase soil nutrient.6. Plants responsed to amendment measures. After the amendments, the similarity coefficient between ground vegetation and soil seed banks increased from 0.318 to 0.370 (single treatments) and 0.455 (compound treatments), specific salt-tolerant plant decreased, plant species with low-salt-resistance increased. Alfalfa seeds which were artificial supplemented germinated in three years, the number of individual plant showed an increase trend.7. Overall consider the indicators of reducing effect of salt and pH, increasing effect of organic matter, plant species and aboveground biomass, the treatment J+W+S laid the pumice showed the best amendment effect for coastal saline soil. |
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